How do doctors and patients make medical decisions? For anyone facing a serious illness, such as heart disease or cancer, this can be a question of life or death. Much of our faith in modern medicine assumes that doctors have accumulated substantial data about the safety and effectiveness of their treatments and that they apply this knowledge rationally to medical decisions, a practice known as evidence-based medicine. But this is only part of the story. Patients, doctors, and researchers know too well that countless other factors influence medical decisions.

Broken Hearts explores these questions by tracing the history of two of the most important treatments in medicine today: coronary artery bypass surgery and coronary angioplasty. Open the book to page 99 and you will find a discussion of the psychology of interventional cardiologists. When asked about their enthusiasm for angioplasty, two Swiss doctors explained that coronary stents “have a great future -- they give excellent predictive results in angiography, are clinically safe, and, most of all, calm the interventional cardiologist.” A Boston cardiologist, in contrast, emphasized not the calming satisfaction of a successful treatment, but the thrill of the procedure itself: “This adrenaline rush is why people like me go into cardiology.” Critics have pointed out that “the financial rush is also sweet, since the median salary for invasive cardiologists is roughly half-a-million dollars.” This leaves patients in a difficult spot. When a doctor recommends a particular treatment, what mix of evidence, psychology, and financial interest is in play? It can be difficult to know.

One of the most important messages of Broken Hearts is that medical practice is far more complicated than patients -- and even doctors -- realize. Medical knowledge is imperfect. What causes heart attacks? Doctors argued for sixty years before settling on the current consensus in the 1990s. Does bypass surgery pose a substantial threat to the brain? Despite a half century of research, experts still disagree. It is essential that patients understand the limits of medical knowledge and the wide range of interests that influence physicians’ thinking. Only then will they be equipped to make the best decisions.